High-resolution multi-turn sensing apparatus and methods

ABSTRACT

High-resolution multi-turn sensing apparatus and methods. A method can be implemented to sense a rotational position of a shaft having a longitudinal axis. Such a method can include determining a turn number of the shaft with a first magnet arranged in a non-contact manner with a first magnetic sensor to allow measurement of a linear position of the first magnet relative to the first magnetic sensor. The linear position can be representative of a turn number of the shaft. The method can further include determining an angular position of the shaft within a given turn with a second magnet positioned at an end of the shaft along the longitudinal axis and arranged relative to a second magnetic sensor. The method can further include combining the turn number with the angular position to generate one or more output signals representative of a measured rotational position of the shaft.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of U.S. application Ser. No. 13/550,167filed Jul. 16, 2012, entitled HIGH-RESOLUTION NON-CONTACTING MULTI-TURNSENSING SYSTEMS AND METHODS, which claims priority to and the benefit ofthe filing date of U.S. Provisional Application No. 61/508,672 filedJul. 17, 2011, entitled DUAL SENSOR HIGH RESOLUTION NON-CONTACTINGMULTI-TURN SENSING SYSTEMS AND METHODOLOGIES, the benefits of the filingdates of which are hereby claimed and the disclosures of which arehereby expressly incorporated by reference herein in their entirety.

BACKGROUND

Field

The present disclosure generally relates to the field of sensors, andmore particularly, to systems and methods for multi-turn non-contactsensing with high-resolution.

Description of the Related Art

In many mechanical and/or electromechanical devices, it is desirable toaccurately determine a state of a rotating object. For example, arotating object such as a jackscrew imparts linear motion to anotherobject by its rotation. In many situations, it is desirable toaccurately determine the linearly moving object's location. Suchdetermination can be based on knowing the angular position of therotating object.

In some applications, it may be desirable to accurately determine therotational position of the rotating object through a plurality of turns.Such a design typically suffers from relatively poor resolution and/orreliance on relatively complex mechanisms.

SUMMARY

In some implementations, the present disclosure relates to a positionsensing device having a rotatable shaft having a longitudinal axis, afirst sensor assembly, and a second sensor assembly. The first sensorassembly includes a first magnet and a first magnetic sensor. The firstsensor assembly is configured to allow measurement of linear position ofthe first magnet relative to the first magnetic sensor so as to allowdetermination of a number of turns of the shaft. The second sensorassembly includes a second magnet and a second magnetic sensor. Thesecond sensor assembly is configured to allow measurement of angularposition of the second magnet relative to the second magnetic sensor soas to allow determination of angular position of the shaft within agiven turn of the shaft, such that an angular resolution associated withthe angular position of the shaft is substantially maintained throughouta plurality of turns of the shaft.

In some embodiments, the linear position of the first magnet can bealong a linear direction having a component substantially parallel tothe longitudinal axis. In some embodiments, the device can furtherinclude a first mechanism configured to couple the first sensor assemblyto the shaft such that rotation of the shaft about the longitudinal axisresults in linear motion of the first magnet along the linear direction.

In some embodiments, the device can further include a second mechanismconfigured to couple the second sensor assembly to the shaft such thatrotation of the shaft results in rotational motion of the second magnetrelative to the second magnetic sensor. The second mechanism can includea magnet holder configured to hold the second magnet and interconnectthe second magnet to an end of the shaft. The second mechanism can beconfigured so that one turn of the shaft results one turn of the secondmagnet.

In some embodiments, the second magnet can be positioned so as to benon-contacting with the second magnetic sensor. The second magnet caninclude a bipolar and diametrally magnetized magnet configured toprovide variable orthogonal and parallel magnetic fluxes to the secondmagnetic sensor.

In some embodiments, the second magnetic sensor can be configured tooperate in quadrature mode. The second magnetic sensor include aplurality of Hall-effect sensors, a plurality of magneto-resistive (MR)sensors, or a plurality of giant magnetic resistive (GMR) sensors. Thesecond magnetic sensor can include four sensors positioned in quadratureand configured to operate as sine-cosine sensors.

In some embodiments, the device can further include an analog interfaceconfigured to process output signals from the second magnetic sensor andyield digital data. By way of an example, the digital data can includeinformation about the angular position of the shaft with a resolution ofat least 10 bits for the given turn of the shaft. By way of a morespecific example, the angular position of the shaft can have aresolution in a range of 10 bits to 14 bits for the given turn of theshaft. Other resolutions, higher or lower than the foregoing examples,can also be implemented.

In some embodiments, the second magnetic sensor and the analog interfacecan be parts of, or disposed on, an application specific integratedcircuit (ASIC).

In some embodiments, the first sensor assembly can be configured toprovide an M-bit resolution sufficient to count the number of turns, andthe second sensor assembly is configured to provide an N-bit resolutionto yield the angular resolution. Combined, the position sensing devicecan have an effective M+N bit resolution over the number of turns.

In some implementations, the present disclosure relates to a method forsensing a position of a shaft rotating about a longitudinal axis. Themethod includes determining a turn number of the shaft by a first magnetarranged in a non-contact manner with a first magnetic sensor to allowmeasurement of a linear position of the first magnet relative to thefirst magnetic sensor. The linear position is representative of the turnnumber of the shaft, with the turn number being determined with an M-bitresolution. The method further includes determining an angular positionof the shaft within a given turn by a second magnet arranged in anon-contact manner with a second magnetic sensor, with the angularposition within the given turn being determined with an N-bitresolution. The method further includes combining the turn number withthe angular position to yield a measured position of the shaft within arange having a plurality of turns.

In some embodiments, the N-bit per turn angular position can besubstantially maintained for the measured position throughout the rangeof plurality of turns. The combining can yield an effective resolutionof M+N bits over the range of plurality of turns.

In some embodiments, the plurality of turns can include more than twoturns. For example, the value of M can be selected to be 4 or less toallow determining of turn numbers up to 16.

In some implementations, the present disclosure relates to a multi-turnsensing apparatus that includes a shaft configured to rotate about alongitudinal axis. The apparatus further includes a rotation counterconfigured to determine a number of turns made by the shaft. Therotation counter includes a first magnet and a first magnetic sensor.The first magnet is coupled to the shaft and configured to move linearlyalong the longitudinal direction when the shaft is rotated. The firstmagnetic sensor is configured to sense the linear motion of the firstmagnet and determine the number of turns of the shaft in a non-contactmanner. The apparatus further includes an angular position sensorconfigured to measure an angular position of the shaft for a given turn.The angular position sensor includes a second magnet and a secondmagnetic sensor. The second magnet is mounted to an end of the shaft andconfigured to rotate with the shaft. The second magnetic sensor isconfigured to sense the rotation of the second magnet and determine theangular position of the shaft in a non-contact manner.

In some implementations, the present disclosure relates to anon-contacting multi-turn sensing device having a first sensor and asecond sensor. Each of the first and second sensors is configured as anon-contacting sensor. The first and second sensors are configured suchthat the device is capable of maintaining a selected angular positionresolution within a range of zero to N turns of an object.

In some embodiments, the first sensor can be configured to allowdetermination of number of turns of the object, and the second sensorcan be configured to allow determination of angular position of theobject within a given turn. In some embodiments, the second sensor canbe configured to determine the position of the object with the selectedangular position resolution. In some embodiments, the selected angularposition resolution can be at least 10 bits. In some embodiments, theselected angular position resolution can be 14 bits. In someembodiments, the first sensor can be configured with a 4-bit measurementrange so as to yield an 18-bit effective angular resolution for thedevice over a range of 0 to 15 turns. Other resolutions, higher or lowerthan the foregoing examples, can also be implemented.

In some implementations, the present disclosure relates to a method forsensing rotation of a rotatable object. The method includes measuring anumber of turns the object rotates. The method further includesmeasuring an angular position of the object within a range of zero to360 degrees when the object has rotated by the number of turns. Themeasure further includes determining a total angular displacement of theobject based on the number of turns and the angular position. The totalangular displacement has an angular resolution substantially equal tothat associated with the angular position measurement.

In some embodiments, the measurement of the number of turns can have anM-bit resolution, and the measurement of the angular resolution can havean N-bit resolution. The total angular displacement resolution can havean M+N bit resolution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows that in some implementations, a positionsensing device can include an angular position sensor and a rotationsensor.

FIG. 2 schematically depicts an example embodiment of a rotation sensor.

FIGS. 3A and 3B show that the rotation sensor of FIG. 2 can beconfigured to mechanically transform an input rotational motion to arange of translational motion of a sensed element such as a magnet whosetranslational position can be detected by a sensing element such as amagnetic field detector.

FIG. 4 schematically shows that in some embodiments, the rotation sensorcan include a processor and a memory to facilitate a programmablecapability.

FIG. 5A shows non-limiting examples of magnet configurations that can beutilized for the magnet of FIG. 2.

FIG. 5B shows that in some embodiments, the magnet can be a permanentdipole magnet positioned so that its magnetization axis is substantiallyperpendicular to the direction of the magnet's longitudinal motion.

FIG. 5C shows that in some embodiments, the magnet can be orientedrelative to its translational motion and the magnetic field detectorsuch that its magnetic axis representative of the field pattern at orabout the detector is generally perpendicular to the translationalmotion direction and generally normal to a plane defined by the magneticfield detector.

FIGS. 6A and 6B show example distributions of magnetic field strengthsfor the configuration of FIG. 5.

FIGS. 7A and 7B show that the example magnet orientation of FIG. 5provides substantial symmetry of the magnet about its magnetic axis soas to reduce sensitivity in alignment of the magnet with respect to themagnetic field detector.

FIGS. 8A and 8B show that the example magnet orientation of FIG. 5 canalso provide reduced sensitivity to misalignments of the magnet alonglateral directions.

FIG. 9 show an exploded view of an example embodiment of the rotationsensor of FIG. 2.

FIG. 10A shows a cutaway perspective view of the rotation sensor of FIG.9.

FIG. 10B shows a cutaway side view of the rotation sensor of FIG. 9.

FIG. 11 shows an assembled perspective view of the rotation sensor ofFIG. 9.

FIG. 12A shows that in some embodiments, a shield can be provided forthe rotation sensor of FIG. 11.

FIG. 12B shows an example situation where an internal component such asthe sensing element of the rotation sensor can be shielded by theexample shield of FIG. 12A.

FIGS. 13A-13F show various non-limiting examples of housing shapes andshield shapes that can be implemented.

FIG. 14 shows an example configuration for calibrating the rotationsensor.

FIG. 15 shows an example of how calibration data can be represented andstored for use during operation of the rotation sensor.

FIG. 16 shows an example calibration process that can be implemented.

FIG. 17 shows that in some embodiments, the rotation sensor can includea rate component configured to calculate, for example, rotational ratebased on sensed angular positions.

FIGS. 18A and 18B show non-limiting examples of feedback control systemsthat can be implemented utilizing the rotation sensor.

FIG. 19 shows an example of an assembled position sensing device havingthe angular position sensor component of FIG. 1 and the rotation sensorcomponent having one or more features of FIG. 2-18.

FIG. 20 shows an exploded view of the example position sensing device ofFIG. 19.

FIG. 21 shows a cutaway view of the example position sensing device ofFIG. 19.

FIGS. 22A and 22B schematically depict side and axial views of anexample of the angular position sensor of FIG. 19.

FIGS. 23A-23D show examples of how the angular position sensor canoperate to yield an angular position of a rotating axis.

These and other aspects, advantages, and novel features of the presentteachings will become apparent upon reading the following detaileddescription and upon reference to the accompanying drawings. In thedrawings, similar elements have similar reference numerals.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

Disclosed herein are example embodiments of a high resolutionnon-contacting position sensing device. As described herein, such asensing device can be designed and implemented in a cost effectivemanner. In some implementations, such a sensing device can be configuredto operate as a multi-turn sensing device.

FIG. 1 schematically shows that in some implementations, a positionsensing device 600 can include an angular position sensor component 602and a rotation sensor component 604. In some implementations, therotation sensor component 604 can be configured to operate in one ormore ways as described in reference to FIGS. 2-18. Details concerningsuch a rotation sensor can also be found in U.S. Patent ApplicationPublication No. 201 1-01 75601 (U.S. application Ser. No. 12/689,047,filed on Jan. 18, 2010), titled “HIGH RESOLUTION NON-CONTACTINGMULTI-TURN POSITION SENSOR” which is expressly incorporated by referencein its entirety. FIGS. 19-23 show examples of how an angular positionsensor component 602 can be combined with the rotation sensor component604 to yield, among others, a high resolution capability over a range ofrotation that can include multiple turns.

As described herein, a rotation sensor can be configured to provideadvantageous features. For example, a rotation sensor can be configuredto provide a multi-turn input capability, and the number of turns forsuch an input can be selected and programmed. Accordingly, rotationalposition resolution of the sensor can be adjusted from relatively coarseresolution to relatively high or fine resolution. In another example, arotation sensor can be configured to provide such functionality withnon-contacting arrangement between a sensing element and a sensedelement. Accordingly, various mechanical issues typically associatedwith physically contacting configurations can be avoided.

In some embodiments, a rotation sensor can be configured to transformrotational motion of a rotating object (such as a shaft) into atranslational motion of a sensed element. A sensing element can beprovided and positioned relative to the sensed element so as to allowdetermination of the sensed element's translational position. In someembodiments, such translational position of the sensed element cancorrespond to a unique rotational position of the shaft.

FIG. 2 shows a rotation sensor 100 that can provide such afunctionality. In some embodiments, some or all of the featuresassociated with the rotation sensor 100 can be implemented in therotation sensor component 604 of FIG. 1.

In some embodiments, the rotation sensor 100 can include a rotatingobject such as a shaft 102 mechanically coupled to a carrier 104. Themechanical coupling can be configured so that rotation of the shaft 102translates to translational motion of the carrier 104. In someembodiments, such a translational motion of the carrier 104 can be asubstantially linear motion along a direction substantially parallel tothe rotational axis of the shaft 102.

In some embodiments, the mechanical coupling between the shaft 102 andthe carrier 104 can include matching screw threads formed on the shaft102 and on the inner surface of an aperture defined by the carrier 104.Additional details of an example of such threaded coupling are describedherein.

In some embodiments, a lead value for the matching threads can beselected so as to provide a mechanical gear ratio between the rotationof the shaft 102 and the translation of the carrier 104. For the purposeof description herein, the term “pitch” may be used interchangeably withthe term “lead” with an assumption that various example screw threadshave single threadforms. It will be understood that one or more featuresof the present disclosure can also apply to screw threads having morethan one threadforms. Thus, if appropriate in the description,distinctions between the two terms may be made.

As shown in FIG. 2, the rotation sensor 100 can further include a magnet106 disposed on the carrier 104 so as to be moveable with the carrier104. Additional details about different orientations of the magnet 106relative to the translational motion direction are described herein.

As shown in FIG. 2, the rotational position sensor 100 can furtherinclude a sensing element 108 configured to sense the magnet 106 atvarious locations along the translational motion direction. Additionaldetails about the sensing element 108 are described herein.

In some embodiments, the rotational position sensor 100 can also includea housing 110 to protect various components, facilitate mounting, etc.Additional details about the housing are described herein.

FIGS. 3A and 3B show that in some embodiments, rotation of the shaft 102in a first direction (arrow 120) can result in the carrier 104 (and themagnet 106) moving linearly in a first direction (arrow 122), based onthe mechanical gear ratio between the shaft 102 and the carrier 104.Rotation of the shaft in the opposite direction (arrow 130) can resultin the carrier 104 (and the magnet 106) moving linearly in a seconddirection (arrow 132) that is opposite the first linear direction 122.

Based on such coupling of the shaft and the carrier, a range (Δα) ofrotational motion (indicated by arrow 140) of the shaft 102 can be madeto correspond to a range (ΔY, indicated by arrow 142) of linear motionof the magnet 106 defined by two end positions (144 a, 144 b) of thecarrier 104. In some embodiments, the linear motion of the carrier 104and/or the magnet 106 can be constrained within the housing 110.Accordingly, the mechanical coupling between the shaft 102 and thecarrier 104 can be selected such that the linear motion range (ΔY)corresponding to the rotational range (Δα) of the shaft 102 is less thanor equal to the mechanically constrained range of the carrier 104 and/orthe magnet 106.

FIG. 3B shows an example coordinate system with “Y” representing thelinear motion direction. It will be understood that the shown coordinatesystem is simply for the purpose of description and is not intended tolimit the scope of the present disclosure in any manner.

FIG. 4 shows that in some embodiments, the rotation sensor 100 caninclude various functional components. As described in reference toFIGS. 2 and 3, a mechanical coupling component 156 can transformrotational movement of the shaft (102) into a linear movement of themagnet (106) that can be represented as a magnet component 158.Positions of the magnet can be detected by the sensor element (108) thatcan be represented as a field sensor component 154.

In some embodiments, the rotational position sensor 100 can also includea processor component 150 and a memory component 152 that can provideone or more functionalities as described herein. In some embodiments,the processor 150 and the memory 152 can provide programmablefunctionality with respect to, for example, calibration and operatingdynamic range of the sensor 100.

As an example, such programmability can facilitate selection of adesired rotational range (depicted as an input 160); and a rotationalposition of the shaft within such a range can be provided with a uniqueoutput value that is within a selected output range (depicted as anoutput 170). Additional details about such programmability are describedherein.

In some embodiments, the magnet 106 depicted in FIGS. 2 and 3 can beconfigured in a number of ways. FIG. 5A depicts non-limiting examples ofmagnets that can be utilized in one or more embodiments of the rotationsensor 100 as described herein. For example, the magnet can be acylindrical shaped magnet (172 a, 172 b, 172 c) or some other shapedmagnet such as a box shaped magnet (172 d, 172 e, 172 f). For thepurpose of description of FIG. 5A, it will be understood that theslanted line fill pattern and the unfilled pattern indicate two poles ofa dipole magnet. For example, the unfilled pattern can represent a northpole, and the slanted line fill pattern can represent a south pole.

In some embodiments, the magnet 106 can be a permanent magnet. In someembodiments, the permanent magnet can be a single dipole magnet or acombination or two or more dipole magnets.

For the purpose of description herein, a permanent magnet can include amagnet that includes a material that is magnetized and generates its ownsubstantially persistent magnetic field. Such materials can includeferromagnetic materials such as iron, nickel, cobalt, and certain rareearth metals and some of their alloys.

For the purpose of description herein, it will be understood that asingle dipole magnet has what are generally referred to as “north” and“south” poles, such that magnetic field lines are designated as goingfrom the north pole to the south pole. For the single dipole magnet, itsmagnetization axis is generally understood to be a line extendingthrough the magnet's north and south poles.

For example, the example magnet 172 a is a cylindrical shaped magnethaving north and south poles along the cylinder's axis. In such aconfiguration, the magnetization axis can be approximately coaxial withthe cylindrical axis.

In another example of a cylindrical shaped magnet 172 b, the north andsouth poles are depicted as being azimuthal halves of the cylinder.Accordingly, its magnetization axis is likely approximatelyperpendicular to the cylindrical axis. In shaped magnets having two ormore dipole magnets (e.g., 172 c, 172 f), a magnetization axis may ormay not form relatively simple orientation with respect to the shape'saxis. For the purpose of description herein, it will be understood thatmagnetization axis can include an overall characteristic of a magnet, aswell as a local characteristic of a magnetic field pattern generated bya magnet.

In some examples described herein, magnetization axis is depicted asbeing generally perpendicular to the longitudinal motion of the magnet.However, it will be understood that other orientations of themagnetization axis are also possible. For example, magnet configurations172 b, 172 c, 172 e, and 172 f can yield non-perpendicular magnetizationaxes when positioned as shown and moved along the indicated Y direction.

FIG. 5B shows that in some embodiments, the magnet 106 can be a dipolemagnet positioned so that its magnetization axis 182 is substantiallyperpendicular to the direction of the magnet's longitudinal motion(depicted as arrow 174). For example, a cylindrical permanent magnet canbe positioned so that its north and south poles are generally form themagnetization axis 182 that is substantially perpendicular to thelongitudinal direction. As described herein, such longitudinal motioncan result from rotation (120, 130) of the shaft 102 to which the magnet106 is coupled. As also described herein, such longitudinal motion canmove the magnet 106 relative to the sensor element 108 so as tofacilitate determination of the magnet's longitudinal position relativeto the sensor element 108.

In the example shown in FIG. 5B, the magnetization axis 182 can begenerally similar to the axis of the magnet's shape (e.g., a cylinder).An example shown in FIG. 5C depicts a more localized view of magneticfield lines 180 generated by the magnet 106. Although the magnet 106depicted in FIGS. 5C-8B are described in the context of a dipole magnetsuch as that shown in FIG. 5B, it will be understood that a similarmagnetic field pattern can be generated or approximated by other magnetconfigurations having one or more dipole magnets. Thus, themagnetization axis 182 depicted in FIG. 5C can be representative of alocal field affecting the sensor element 108.

In some embodiments, the magnet 106 can be oriented such that itsmagnetization axis 182 representative of magnetic field at or about thesensor element 108 is generally perpendicular to the translationalmotion direction. In some embodiments, the magnet 106 can be positionedso that the magnetization axis and the longitudinal axis generallydefine a plane that extends through an approximate center of the sensorelement 108. In the context of the example coordinate system shown inFIG. 3B, the magnetization axis of the magnet 106 is generally along theZ axis in such embodiments. As described herein, such a configurationcan provide features that are desirable.

FIG. 5C shows a more detailed view of a pole section of the magnet 106relative to a side view of the sensor element 108. As shown, themagnetization axis 182 of the magnet 106 is depicted as being generallyperpendicular to a plane defined by the sensor element 108.

Also shown are depictions of magnetic field lines 180 generated by themagnet 106. Assuming that the shown pole is a magnetic north pole,several field vectors are depicted in their decomposed (B_(Z) and B_(Y))forms (in the example coordinate system shown in FIG. 3B). As shown,field vectors 184 are generally symmetrical about the magnetization axis182. Thus, the Z component of the field vector 184 a is generally samein direction and magnitude as the Z component of the field vector 184 d;and the Y component of the vector 184 a is opposite in direction butgenerally same in magnitude as the Y component of the vector 184 d.Similarly, the field vector 184 b is generally a mirror image of thefield vector 184 c.

Based on the foregoing, average contribution of B_(Z) is generallysymmetric about some Y=0 as the magnet moves along the Y direction. Suchsymmetry is depicted as a B_(Z) curve 190 in FIG. 6A. If the B_(Z)component alone is measured by the sensor element 108, then there may ormay not be ambiguity in magnet's position determination. For example, ifthe sensor element 108 and the magnet 106 are configured so that themagnet's motion is limited to one longitudinal side of the sensorelement, the measured B_(Z) component may be that of the Y>0 portion ofthe curve 190. In such a situation, there is likely no ambiguity inposition determination based on the B_(Z) component alone. However, ifthe sensor element 108 and the magnet 106 are configured so that themagnet's motion is allowed on both longitudinal sides of the sensorelement, there can be an ambiguity in position determination that can beresolved.

In some embodiments, magnetic field component along the translationalmotion direction (B_(Y)) can be measured simultaneously with the B_(Z)component. Based on the example field representations 184 in FIG. 5C,the average contribution of B_(Y) is generally asymmetric about some Y=0as the magnet moves along the Y direction. Such asymmetry is depicted asa B_(Y) curve 192 in FIG. 6B. Thus, the B_(Z) ambiguity about Y=0 can beresolved by the asymmetry where B_(Y)>0 when Y>0 and B_(Y)<0 when Y<0.

In some embodiments, it is possible to characterize the magnet'sposition along the Y direction based on the values of BY component.However, utilizing the B_(Z) component can be advantageous for a numberof reasons. For example, detection of perpendicular component (relativeto a magnetic field detection plane) is usually preferred over othercomponents. In another example, the B_(Y) curve 192 passes through azero value at Y=0. Thus, at Y=0 and near Y=0, the B_(Y) component has avalue of zero or a value that is relatively small. Consequently,signal-to-noise ratio can be unacceptably low at what can be amid-portion of the magnet's travel along the Y direction. In contrast,the B_(Z) component has a maximum value at generally the samemid-portion of the magnet's travel along the y direction. Further, themaximum value of the B_(Z) component can be typically significantlyhigher than the maximum value of the B_(Y) component.

In addition to the foregoing features, there are other considerationsfor which the example magnet orientation of FIG. 5C can provideadvantageous features. Such features can include relative insensitivityof the output (170 in FIG. 4) to various deviations in the magnet'sorientation.

FIGS. 7A and 7B show the magnet 106 mounted on the carrier 104, andviewed along the magnetization axis. For such an example configuration,mounting can be achieved by the carrier 104 defining a recess (262 inFIG. 9) shaped similar to at least a portion of the magnet 106 (e.g.,cylindrical shaped recess to receive cylindrical shaped magnet). In thecontext of such an example mounting configuration, FIGS. 7A and 7B showthat due to the generally symmetric magnetic field, azimuthalorientation of the magnet 106 with respect to the magnetization axis(parallel to Z-axis in FIGS. 7A and 7B) generally does not affect themagnetic field 180 reaching the sensor element (108 in FIG. 5C). For thepurpose of showing different azimuthal orientations, an indicator 200 isdepicted on the magnet 106.

In some embodiments, the magnet 106 is preferably mounted on the carrier104 so that the magnet's magnetization axis is substantially along theZ-axis, and thus perpendicular to both X and Y axes. Due to variousreasons, however, the magnetization axis may deviate from the Z-axis;and examples of such deviations are depicted in FIGS. 8A and 8B.

In FIG. 8A, a side view of the magnet-carrier assembly shows that themounted magnet's axis 182 deviates from the Z-axis (indicated as 210) toresult in the magnet 106 being tilted along the Y direction. In FIG. 8B,an end view of the magnet-carrier assembly shows that the mountedmagnet's axis 182 deviates from the Z-axis (indicated as 210) to resultin the magnet 106 being tilted along the X direction. In somesituations, the magnet 106 can be tilted so as to yield a combination ofX and Y tilts of FIGS. 8A and 8B.

If the magnet 106 is tilted in the foregoing manner, the magnetic fieldpatterns may deviate from the ideal pattern depicted in FIGS. 6A and 6B.Because the B_(Z) component is relatively large compared to the B_(Y)component, and because the deviation angle (relative to Z-axis) isrelatively small, the net effect on B_(Z) can be relatively small.Further, even if there are significant deviations in B_(Z) and/or B_(Y)components, programmability in some embodiments as described herein canaccount for such deviations and thus make the output even less sensitiveto magnet orientation.

FIGS. 9-11 show various views of an example configuration of therotation sensor 100. FIG. 9 shows an exploded view 220; FIG. 10A showsan assembled cutaway perspective view 300; FIG. 10B shows an assembledcutaway side view 310; and FIG. 11 shows an assembled perspective view320.

As shown, the shaft 102 includes a first end 230 configured tofacilitate transfer of torque to the shaft 102 from an externalcomponent (not shown). In the example shown, the first end 230 defines aslot 302 (FIG. 10A) for such a purpose. It will be understood that anumber of different configurations are possible.

The shaft 102 also includes a second end 232 configured to couple withthe carrier 104. In the example shown, the second end 232 of the shaft102 and a matching aperture 260 of the carrier 104 define matchingthread patterns that facilitate translational motion of the carrier 104in response to rotation of the shaft 102.

The second end 232 of the shaft 102 is shown to be dimensioned toreceive a retaining clip 256 for limiting travel of the carrier 104. Thesecond end 232 is also shown to include a tip 234 (FIG. 10A) dimensionedto be received by a similarly dimensioned recess 304 defined by an endcap 272 so as to constrain the second end 232 of the shaft.

In the example shown, a portion between the first and second ends (230,232) of the shaft 102 is dimensioned to be supported within an aperture252 defined by a sleeve 250. The sleeve 250 in turn is dimensioned to besecured to the housing 110 via a bushing 240 and a washer 254. Thus,supports of the shaft 102 by the sleeve 250 and the recess 304 of theend cap 274 allow the shaft to rotate with relative precision withrespect to the housing 110. Further, longitudinal motion of the shaft102 with respect to the bushing 240 (and thus the housing 110) isinhibited by a retaining washer 242 and the washer 254.

In some embodiments, the bushing 240 can include external screw threadsthat mate with a mounting nut 244 to allow mounting of the sensorassembly. As shown in FIG. 10B, the thread pattern on the bushing can beselected to provide an adjustable space 312 between the mounting nut 244and the housing to facilitate mounting to various dimensioned structuressuch as plates. A washer 246 can further facilitate such mounting.

In some situations, it may be desirable to have the overall shape of thesensor assembly to be in certain form. For example, a design may callfor a rounded form of housing (when viewed longitudinally). Moreparticularly, a design preference may call for a circular shaped housingwith respect to the longitudinal axis of the shaft. However, if theinterior of the housing is circularly shaped and the carrier is shapedcircularly also with the shaft extending through the carrier's center,the carrier's rotational tendency (in response to the shaft rotation)may not be inhibited in absence of some rotation-inhibiting features.

Thus, in some embodiments, a side wall 207 of the housing 110 can beshaped in a “U” shape (when viewed longitudinally), and the carrier canbe shaped accordingly. In some embodiments, the curved portion of the“U” can be substantially semi-circular in shape, and the longitudinalaxis of the shaft 102 can be positioned at the center of a circle thatwould be formed by two of such semi-circles. Such a configuration canaccommodate at least some of the aforementioned circular designpreference. In some embodiments, the sides of the “U” can extend upwardso as to inhibit the rotational tendency of the carrier 104.

In some embodiments, the top portion of the “U” shaped side wall 207 canbe generally flat so as to accommodate a circuit assembly 280 that canbe formed on a flat circuit board. In the example shown, the circuitassembly 280 can be formed as a substantially complete unit on a printedcircuit board that is dimensioned to slide into grooves 276 formed nearthe top portion of the side wall 270.

In some embodiments, as shown in FIG. 9, the example carrier 104 canalso have a “U” shape to fit into the side wall 270 and slidelongitudinally therein in response to the rotation of the shaft 102.Similar to the side wall 270, the top portion of the carrier 104 can begenerally flat so as to accommodate the flat shaped circuit assembly280. The height of the carrier's “U” shape can be selected so as toallow mounting of the magnet 106 thereon (via the recess 262) at adesired Z distance (see the example coordinate system in FIG. 3B) fromthe sensing element 108.

As shown, the circuit assembly 280 can include one or more electricalcontacts 282, and such contacts can be allowed to extend out of thehousing 110 through appropriately formed holes on the end cap 272. Insome embodiments, a sealing member 274 can be provided so as tofacilitate assembly of the rotational sensor device, as well as provideat least some sealing functionality for various components inside of thehousing 110. Such sealing member can include a gasket, an epoxy, or somecombination thereof.

FIG. 11 shows an assembled perspective view 320 of the rotationalposition sensor. One can see that the example configurations andarrangements of various components as described herein allow therotational position sensor to provide magnetic field sensingfunctionality in a relatively simple and compact packaging whilesatisfying certain design criteria.

In some embodiments, as shown in FIGS. 11 and 12A, the side wall 270 ofthe housing can include slots 324 dimensioned to facilitate easymounting and removal of a shield 290. In some situations, the rotationalposition sensor can be subjected to external electric and/or magneticfields, and/or radiation.

Because the sensor element 108 operates by sensing magnetic fields, itis desirable to limit magnetic fields to those from the magnet 106 foraccurate measurements. Thus, in some embodiments, the shield 290 can beformed of material that has relatively high magnetic permeability. Forexample, metal alloys such as Permalloys and Mu-metals can be used toform the shield 290.

As shown, the shield 290 can be shaped to substantially conform to theupper portion 322 of the side wall 270. In some embodiments, a cover 292can be dimensioned to have its edges slide into the slots 324 andsandwich the shield 290 between the cover 292 and the upper portion 322of the side wall 270. In some embodiments, the cover 292 can be formedrelatively easily from plastic to accommodate its shape that is morecomplex than the shield 290 (to fit into the slots 324).

In some operating conditions, the rotational position sensor may besubjected to radiation such as X-ray, gamma radiation, energetic chargedparticles, neutrons, and/or other ionizing radiations. Such radiationcan have detrimental effects on one or more parts of the rotationalsensor, especially upon prolonged exposure. For example, in embodimentswhere the sensor element 108 is formed from or based on semiconductormaterials and/or components, exposure to radiation can degrade thesensing performance.

FIG. 12B shows that in some embodiments, the example shield 290 canprovide effective shielding of the sensor element 108 from radiation 328without having to fully enclose the housing 270. In common situationswhere the general direction of radiation 328 is known, the rotationalposition sensor can be oriented so that the shield 290 covers the sensorelement 108 and/or other component(s) from the radiation so as to reducetheir exposure.

For example, suppose that a rotational position sensor is being used tomonitor the position of a movable patient platform for a radiation basedtreatment or imaging device. Many of such platforms are moved viajackscrews, and monitoring of the rotation of such jackscrews (by therotational position sensor) can provide information about the platformposition. In such controlled clinical situations, direction and amountof radiation associated with the treatment or imaging device aregenerally well known. Thus, the rotational position sensor (with ashield) can be oriented so as to provide shielding effect from theradiation.

In some embodiments, the radiation shield 290 can be formed from anddimensioned to provide shielding effect from particular radiation byattenuating intensity of such radiation. Materials such as lead havingheavy nuclei can be suitable for shielding X-ray and gamma radiation;whereas low density materials such as plastic or acrylic glass can besuitable for energetic electrons. Other materials for other types ofradiations are also possible.

As described herein, use of such easily installable and removableshields can provide an advantageous feature in the context of radiationsafety. Because the internal components are shielded from performancedegrading radiation, the rotational position sensor can have a longerservice life. In the event that the shield needs to be replaced due toits own activated radiation from prolonged exposure, the shield can bereplaced relatively easily; and the radioactive shield can be stored ordisposed of safely easily due to its relatively small size and simpleform.

FIGS. 13A-13F show various non-limiting examples of the housing 270 thatcan be used as part of the rotational position sensor. Also shown arenon-limiting example configurations of the shield 290 having one or morefeatures as described herein.

FIG. 13A shows an example housing configuration 500, where the housing270 includes a curved wall 502, and first and second walls 504 a, 504 bthat extend from the curved wall 502 so as to form a “U” shaped wall.Examples of advantageous features that can be provided by U-shaped wallsare described herein in reference to FIGS. 9 and 10.

FIG. 13A further shows that in some embodiments, the carrier 104 can beshaped to generally conform to and move longitudinally relative to theinterior of the U-shaped wall. Various features of the carrier 104(e.g., coupling with the shaft 102, and holding of the magnet 106 so asto allow longitudinal movement relative to the sensor element 108) aredescribed herein.

FIG. 13B shows that in some embodiments, the curved wall can be definedby a portion of a circle 516. For example, in an example housingconfiguration 510, the curved wall can be defined by a semi-circle 512that is part of the shown circle 516. In some embodiments, the portionof the circle defining the curved wall can be an arc that extends moreor less than approximately 180 degrees associated with the semi-circle.In the example shown in FIG. 13B, the center of the circle 516 thatdefines the semi-circle wall 512 can be substantially concentric withthe center of the shaft 102.

As further shown in FIG. 13B, first and second walls 514 a, 514 b canextend from the semi-circular wall 512 so as to form a U-shaped wall ofthe housing 270. In some embodiments, the carrier 104 can be formed soas to substantially conform to the interior of the curved portion of theU-shaped wall. For example, the curved portion of the carrier 104 can bedefined by a semicircle that is part of the depicted circle 518 so as toconform to the example semi-circle wall 512.

FIGS. 13C and 13E show that the top portion of the U-shaped housing canbe configured in a number of different ways. An example configuration520 of FIG. 13C shows that a cap wall 524 can be coupled with the sidewalls (e.g., 514 a, 514 b in FIG. 13B) so as to form substantiallysquare corners indicated as 522 a and 522 b. Another exampleconfiguration 540 of FIG. 13E shows that a cap wall 544 can be coupledwith the side walls (e.g., 514 a, 514 b in FIG. 13B) so as to formrounded corners indicated as 542 a and 542 b.

FIGS. 13D and 13F show that the shield 290 having one or morefunctionalities as described herein can be shaped in a number of ways.An example configuration 530 of FIG. 13D shows that the shield 290 canbe shaped to generally conform to the example square-cornered (522 a,522 b) top portion of the housing of FIG. 13C, such that the shield 290includes generally square corners indicated as 532 a and 532 b. Anotherexample configuration 550 of FIG. 13F shows that the shield 290 can beshaped to generally conform to the example rounded-cornered (542 a, 542b) top portion of the housing of FIG. 13E, such that the shield 290includes rounded corners indicated as 552 a and 552 b.

For the purpose of description of FIGS. 13A-13F, it will be understoodthat terms such as “top” and “side” are used in the context of relativepositions of different parts associated with the U-shaped wall, andshould not be construed to mean that the rotational position sensor as awhole needs to be positioned as such. For clarity, it will be understoodthat for embodiments of the rotational position sensor having theU-shaped housing, the sensor can be oriented in any manner (e.g., “U”opening up, down, sideway, or any combination thereof) as needed ordesired.

As described herein in reference to FIG. 4, some embodiments of therotational position sensor 100 can include a programmable functionalitywith respect to, for example, calibration and operating dynamic range ofthe sensor 100. FIGS. 14 and 15 show examples of such programmability.

In FIG. 14, a calibration system 330 can include a controller 332 incommunication (depicted as line 334) with an actuator 336 so as to allowcontrolled rotation (arrow 338) of the shaft 102. In response to thecontrolled rotations (e.g., in steps), the magnet 106 is depicted asmoving relative to the sensor element 108 in a selected longitudinalmotion range (depicted as 350) within the housing 110. At each of thecontrolled magnet positions, an output signal can be collected throughthe contacts 282 via a connector 342, and such signal can be provided(line 340) to the controller 332 for processing.

The calibration data 360 obtained in the foregoing manner can berepresented in a number of ways. As shown in an example representation360 in FIG. 15, a relationship between an output such as voltage and aninput such as an angular position α can be obtained. For a plurality ofcalibration data points 362 obtained at a number of angular positions(e.g., obtained in increments of Δα), a curve such as a linear line 380can be fit to represent a relationship between the output voltage andthe input angular position. Fitting of such representative curve can beachieved in a number of ways that are generally known.

In some situations, some portion(s) of the calibration data points maydeviate systematically from a representative curve. For example, datapoints near the upper limit of the angular position α are depicted asdeviating from the linear line 380 (representative of the main portionof the angular range). Such deviation can occur due to a number ofreasons. For the purpose of description, the systematic deviation isshown as being represented by a deviation curve 370.

In some embodiments, one or more corrections can be made so as to adjustan output so as to yield a desired output representation. For example,the systematic deviation 370 can be adjusted (arrow 372) such that theoutput voltage can be represented as a substantially linear relationshipwithin a defined range of the angular position α.

In some embodiments, information about the calibrated input-to-outputrelationship can be stored so as to be retrievable during operation ofthe rotational position sensor 100. For example, such information can bestored in the memory component 150 of FIG. 4 in one of a number offormats, including, a lookup table, one or more parameters (e.g., slopeand intercept parameters if linear relationship is used) for analgorithm representative of the relationship, etc.

FIG. 16 shows an example process 400 that can be implemented to achieveone or more features of the calibration process described in referenceto FIGS. 14 and 15. In a process block 402, the shaft of the angularposition sensor 100 can be rotated to a first position (α₁)representative of a first limit (e.g., lower limit) of a desired rangeof rotational motion. The process 400 then can enter an iterativesequence where measurements are taken at incremental steps. Thus, in adecision block 404, the process 400 determines whether the currentangular position α is less than a second position (α₂) representative ofa second limit (e.g., upper limit) of the desired range of rotationalmotion. If the answer is “Yes,” the process 400 continues with anotheriteration of measurement. In a process block 406, a calibrationmeasurement can be obtained at the current shaft position α. In aprocess block 408, the shaft position can be incrementally changed byΔα, and the process 400 can perform the test of the decision block 404with the updated angular position.

If the answer in the decision block 404 is “No,” a systematic correction(if any) can optionally be applied in a process block 410. In a processblock 412, a representative output response (e.g., a linear outputresponse) can be obtained. In a process block 414, information about therepresentative output response can be stored so as to allow retrievaland use during operation of the angular position sensor 100.

In some embodiments, the calibration feature can include a lockingfeature to inhibit unauthorized calibration and/or altering of theinformation about the output response. In some situations, such lockingcan occur after a calibration process performed at an authorizedfacility such as a fabrication facility.

In some situations, it may be desirable to provide at least somecapability for adjustments, customizations, and the like after lockingof the calibration feature and/or calibration information. In someembodiments, the calibration feature can further include a key (e.g., anelectronic key) that allows an authorized party to unlock at least someof such functionalities. Locking, unlocking, and related operations forthe foregoing can be achieved in known manners.

In the foregoing description in reference to FIGS. 14-16, a linearrelationship between an output and an input is described as being one ofa number of possible relationships. In some embodiments, such linearrelationship can arise from a translational position of the magnetrelative to the sensing element 108.

For example, in some embodiments, the sensing element 108 can be anintegrated circuit having capability to detect three components (B_(X),B_(Y), B_(Z)) of a magnetic field. Such an integrated circuit (IC) caninclude, for example, a Hall sensing monolithic sensor IC (modelMLX90333) manufactured by Melexis Microelectronic Systems. Additionalinformation about the example IC-based sensor element can be found invarious documentations (including an application note) available at themanufacturer's website http://melexis.com.

For sensor elements having capability to detect two or more magneticfield components (such as the example Melexis sensor), a combination ofB_(Z) and a longitudinal component (e.g., B_(Y)) can yield a quantitythat has an approximately linear relationship with longitudinal positionof the magnet (relative to the sensor element). For example,θ=arctan(B_(Y)/B_(Z)) (θ defined as shown in FIG. 5C) can yield anapproximately linear response to longitudinal position of the magnetalong the Y-axis.

In some embodiments, such an approximately linear relationship betweenthe example quantity θ and Y position can be extended to obtain anapproximately linear relationship between the quantity θ and angularposition (α) of the shaft. Such extension of the relationship can bemade readily, since the angular position (α) of the shaft generally hasa linear relationship with translational motion of the magnet carriercoupled via substantially uniform threads.

In some embodiments, the example linear relationship between the angularposition (α) of the shaft and the magnetic field quantity θ can beprovided with an amplitude parameter that allows selection of a desiredoutput range. For example, the amplitude parameter can be selected so asto yield output values in a range between approximately 0 and 5 volts.

Although the foregoing example is described in the context of agenerally linear property that can result from some combination ofmagnetic field components, it will be understood that such detectedquantities do not necessarily need to be linear to begin with. Forexample, the example B_(Y) and/or B_(Z) components described inreference to FIG. 6 can be linearized by applying generally knowntechniques to calibration data points and/or representative curves.

In some embodiments, an output of the rotational position sensor 100does not even need to be a linear response to the input rotation.Preferably, however, each angular position of the shaft has a uniquecorresponding output.

In various examples described herein, an output of the rotationalposition sensor 100 is sometimes described as being a voltage. It willbe understood, however, that the output can be in a number of differentforms. The output can be in either digital or analog format, and includebut not limited to signals based on pulse width modulation or serialprotocol.

In some embodiments, the output of the rotational position sensor 100can be in a processed format. Such processing can include, for example,amplification and/or analog-to-digital conversion.

In some embodiments, sensing of translational position of the magnet(and thus angular position of the shaft) can allow determination of arate in which such a position changes. Thus, as depicted schematicallyin FIG. 17, a sensor system 420 can include a position determinationcomponent 422 having features as described herein, and optionally a ratecomponent 424. In some embodiments, the rate component can be configuredto determine an average or an approximation of instantaneous rotationalspeed of the shaft by combining the position measurements as describedherein with time information (e.g., sampling period). In someembodiments, such a rate determination can be extended to estimation ofangular acceleration of the shaft.

FIGS. 18A and 18B schematically depict non-limiting examples of systemswhere the rotational position sensor can be used. In one example system430 shown in FIG. 18A, a rotational position sensor 440 can be disposedbetween an actuator 432 and a controlled device 444 being mechanicallydriven by the actuator 432 via a mechanical coupling 436. Thus,mechanical output (arrow 434) of the actuator 432 can be coupled (arrow438) to the sensor 440 (via, for example, the shaft), and thatmechanical actuation can continue through the sensor 440 and betransmitted (arrow 442) to the controlled device 444.

The sensor 440 can operate as described herein so as to facilitatedetermination of, for example, the rotational state of the mechanicalcoupling (e.g., rotational position of the shaft). As shown, the sensor440 can be in communication with a controller 450 configured to control(line 452) the actuator 432 in response to the sensor's output. In someembodiments, such sensing and controlling of the actuator 432 (and thusthe controlled device 444) can be configured as a feedback controlsystem.

FIG. 18B shows another example system 460 that can be a variation to thesystem of FIG. 18A. In the example configuration 460, a mechanicalcoupling component 466 can be configured to receive mechanical output(arrow 464) from an actuator 462 and provide separate mechanical outputs472 and 468. The output 472 can be provided to a controlled device 474,and the output 468 can be provided to a sensor 470. Similar to theexample system 430 of FIG. 18A, the sensor 470 can provide an output 434to a controller 480 configured to control (line 482) the actuator 462.Again, such sensing and controlling of the actuator 462 can beconfigured as a feedback control system.

As described in reference to FIGS. 18A and 18B, the exampleconfiguration 430 can be considered to be an inline type monitoringsystem, and the example configuration 460 can be considered to be aparallel type monitoring system. Other monitoring and/or feedbackconfigurations are also possible.

Although described in the context of the example rotation sensor 100 ofFIGS. 2-18, it will be understood that one or more features of thepresent disclosure can be implemented with other rotation sensordesigns. In the example context of the rotation sensor 100 (of FIGS.2-18), the position sensing device 600 of FIG. 1 can be implemented as adevice 610 shown in FIGS. 19-21. FIG. 19 shows an assembled view of thedevice 610; FIG. 20 shows an exploded view of the device 610; and FIG.21 shows a cutaway view of the device 610.

As shown in the exploded view of FIG. 20, the rotation sensor 604 ofFIG. 1 can be implemented as a sensor assembly 630. Additional detailsabout such a sensor assembly are described herein in reference to FIGS.2-17.

FIGS. 20 and 21 show that in some embodiments, the angular positionsensor 602 of FIG. 1 can be implemented as a sensor assembly 620. Theangular position sensor 620 can include a magnet 702 mounted to arotatable axis 632 of the device 610 via a mounting member 704. Theangular position sensor 620 can further include a magnetic sensor 700mounted on a circuit board 706. In some embodiments, the angularposition sensor 620 can be configured to be a part of an applicationspecific integrated circuit (ASIC). In some embodiments, the magnet 702and the magnetic sensor 700 can be positioned relative to each other soas to be substantially non-contacting. Additional details and examplesassociated with the magnet 702 and the magnetic sensor 700 are describedherein in greater detail.

FIGS. 22A and 22B schematically depict isolated side and axial views ofan example configuration 720 of a magnet 722 (702 in FIGS. 20 and 21)and its non-contacting position relative to a magnetic sensor 726 (700in FIGS. 20 and 21). The magnet 722 is shown to be mounted to arotatable axis 724 (632 in FIG. 21). In FIGS. 22A and 22B, a magnetholder (e.g., 704 in FIGS. 20 and 21) is not shown.

In some embodiments, the magnet 722 can be a bipolar and diametrallymagnetized so as to yield variable orthogonal and parallel magneticfluxes to the magnetic sensor 726. In some embodiments, such a magnetcan be separated from the magnetic sensor by, for example, approximately1 mm ±0.5 mm working distance, and the magnetic sensor 726 can beconfigured to read the angular position of the magnet 722 with 10 to 14bit resolution. Other separation distances and/or other resolutioncapabilities can also be utilized.

FIGS. 23A-23D show examples of how such magnetic flux can be detected soas to determine the angular position of the magnet 722 of FIGS. 22A and22B (and thus the rotatable axis 724) relative to the magnetic sensor726. In some implementations, the magnetic sensor 726 can include aquadrature Hall-effect sensor assembly 752 having Hall-effect sensorsindicated as H1-H4. Such Hall-effect sensors may or may not be formed asintegrated sensors. Although the magnetic sensor 726 is described in thecontext of Hall-effect sensors, it will be understood that other typesof sensors can also be implemented. For example, sine-cosinemagneto-resistive (MR) sensors or giant magnetic resistive (GMR) sensorscan be utilized (e.g., in a bridge configuration).

FIG. 23A shows that in some implementations, the magnetic sensorassembly 752 can be configured to operate as a sine-cosine sensor, wherethe variations of the orthogonal and parallel magnetic fluxes (e.g., 760in FIG. 23B) at the magnetic sensor assembly 752 can be approximated assine and cosine in quadrature. Such outputs of the Hall-effect sensorscan be processed by an analog interface 750 configured to providefunctionalities such as amplification and conditioning (754) andconversion to digital data (756) so as to yield one or more outputs(758). In some embodiments, the back-end portion of the foregoingreadout arrangement can be configured so as to provide programmableinterface with A/D, D/A and serial communication capabilities.

In the example shown in FIGS. 23A and 23B, the Hall-effect sensors H1-H4are depicted as outputting +sine, +cosine, −sine, −cosine signals,respectively. Such signals can be based on Hall voltages (V_(H))resulting from interactions of the currents (I) with the magnetic fields(B). Accordingly, sensing of such signals can yield flux values H1-H4that can be represented as follows:

H1=â·sin(α)   (1a)

H2=â·cos(α)=â·sin(α+90°)   (1b)

H3=−â·sin(Ε)={circumflex over (α)}·sin(α+180°)   (1c)

H4=−â·cos(α)={circumflex over (a)}·sin(α+270°),   (1c)

such that:

H1−H3=2â·sin(α)   (2a)

H2−H4=2â·cos(α).   (2b)

Upon differential readouts, the signals can be approximated as sine andcosine signals. Such signals can be used to calculate an angulardisplacement (A) of the magnet relative to the magnet sensor. Forexample, the quantity A can be estimated as follows:

(H1−H3)/(H2−H4)=(2â·sin(α))/(2â·cos(α))=tan(α)   (3a)

A≈arctan((H1−H3)/(H2−H4))=arctan(tan(α))=α.   (3b)

Thus, as shown in FIG. 23C, readouts of sine and cosine signals (784,780) in quadrature can yield an angular displacement (A) of the magnetthat can be estimated as being linear with the phase angle α. Suchlinear estimation is depicted by sloped lines 782, 786 and 788.

In some situations, the Hall sensors' amplitudes may change due toeffects such as mechanical misalignment, internal magnetic fieldvariation, temperature variation, and/or external magnetic fields.However, as shown in FIG. 23D, such effects will likely affect thesignals amplitudes and not the sin/cos ratios. Thus, the foregoingexample of estimating the angular displacement by the sin/cos ratio orthe phase angle a can yield a stable sensor.

Referring to the example device 610 of FIGS. 19-21, suppose that theangular position sensor 620 yield an angular displacement value A asdescribed above in a range of 0 to 360 degrees. Further, suppose thatsuch an angular displacement value A can be measured with a resolutionof, for example, 14 bits. In some implementations, fine resolution ofthe device 610 can be provided by the angular position sensor 620, andthe rotation sensor 630 can be configured with relatively low resolution(e.g., 4 bits) to count the number of turns made by the rotatable axis632. Such a configuration can maintain the per-angle resolution providedby the angular position sensor 620 throughout a full range of rotationalmotion, which in some situations can involve multiple turns of therotatable axis 632. Accordingly, the rotation sensor 630 operating as aturn counter, in combination with the high resolution capability of theangular position sensor 620, can yield a high resolution positionsensing device over a wide range of rotational motion.

In the foregoing example where the angular position sensor 620 isconfigured to provide a 14-bit resolution and the rotation sensor 630 isconfigured to provide a 4-bit capability, the rotation sensor 630 iscapable of determining the number of turns from 0 to 15. Within eachturn, the angular position sensor 620 can provide an angular resolutionof about 0.02 degree (360/(2**14)). Because the rotation sensor 630 isproviding the turn number information, angular position in any of theturns within the range of 0 to 15 can benefit from the 0.02 degreeresolution. Accordingly, the angular resolution for the entire range ofmotion remains at 0.02 degree, effectively yielding an 18-bit angularresolution over a range of 0 to 15 turns, inclusive.

If the angular position sensor 620 is not used, then the angularresolution of the device 610 can depend on the rotation sensor 630operating in the linear-position sensing mode (as described in referenceto FIGS. 2-18). In such a mode, increasing the number of turns caninvolve increasing the bit resolution to maintain a given angularresolution.

Thus, as described herein, combination of an angular position sensor(e.g., 620) and a rotation sensor (e.g., 630) configured to include turncounting capability can yield a device having a high angular resolutionover multiple turns. It will be understood that one or more conceptsdescribed herein can be implemented in other configurations. Forexample, counting of turns can be provided by some other sensing device.Further, angular displacement can be measured by using one or more othertechniques.

In some embodiments, some or all of various features such as shielding,housing, and/or calibration associated with the rotation sensordescribed in reference to FIGS. 2-18 can be implemented in the positionsensing device 610 described in reference to FIGS. 19-21.

The present disclosure describes various features, no single one ofwhich is solely responsible for the benefits described herein. It willbe understood that various features described herein may be combined,modified, or omitted, as would be apparent to one of ordinary skill.Other combinations and sub-combinations than those specificallydescribed herein will be apparent to one of ordinary skill, and areintended to form a part of this disclosure. Various methods aredescribed herein in connection with various flowchart steps and/orphases. It will be understood that in many cases, certain steps and/orphases may be combined together such that multiple steps and/or phasesshown in the flowcharts can be performed as a single step and/or phase.Also, certain steps and/or phases can be broken into additionalsub-components to be performed separately. In some instances, the orderof the steps and/or phases can be rearranged and certain steps and/orphases may be omitted entirely. Also, the methods described herein areto be understood to be open-ended, such that additional steps and/orphases to those shown and described herein can also be performed.

Some aspects of the systems and methods described herein canadvantageously be implemented using, for example, computer software,hardware, firmware, or any combination of computer software, hardware,and firmware. Computer software can comprise computer executable codestored in a computer readable medium (e.g., non-transitory computerreadable medium) that, when executed, performs the functions describedherein. In some embodiments, computer-executable code is executed by oneor more general purpose computer processors. A skilled artisan willappreciate, in light of this disclosure, that any feature or functionthat can be implemented using software to be executed on a generalpurpose computer can also be implemented using a different combinationof hardware, software, or firmware. For example, such a module can beimplemented completely in hardware using a combination of integratedcircuits. Alternatively or additionally, such a feature or function canbe implemented completely or partially using specialized computersdesigned to perform the particular functions described herein ratherthan by general purpose computers.

Multiple distributed computing devices can be substituted for any onecomputing device described herein. In such distributed embodiments, thefunctions of the one computing device are distributed (e.g., over anetwork) such that some functions are performed on each of thedistributed computing devices.

Some embodiments may be described with reference to equations,algorithms, and/or flowchart illustrations. These methods may beimplemented using computer program instructions executable on one ormore computers. These methods may also be implemented as computerprogram products either separately, or as a component of an apparatus orsystem. In this regard, each equation, algorithm, block, or step of aflowchart, and combinations thereof, may be implemented by hardware,firmware, and/or software including one or more computer programinstructions embodied in computer-readable program code logic. As willbe appreciated, any such computer program instructions may be loadedonto one or more computers, including without limitation a generalpurpose computer or special purpose computer, or other programmableprocessing apparatus to produce a machine, such that the computerprogram instructions which execute on the computer(s) or otherprogrammable processing device(s) implement the functions specified inthe equations, algorithms, and/or flowcharts. It will also be understoodthat each equation, algorithm, and/or block in flowchart illustrations,and combinations thereof, may be implemented by special purposehardware-based computer systems which perform the specified functions orsteps, or combinations of special purpose hardware and computer-readableprogram code logic means.

Furthermore, computer program instructions, such as embodied incomputer-readable program code logic, may also be stored in a computerreadable memory (e.g., a non-transitory computer readable medium) thatcan direct one or more computers or other programmable processingdevices to function in a particular manner, such that the instructionsstored in the computer-readable memory implement the function(s)specified in the block(s) of the flowchart(s). The computer programinstructions may also be loaded onto one or more computers or otherprogrammable computing devices to cause a series of operational steps tobe performed on the one or more computers or other programmablecomputing devices to produce a computer-implemented process such thatthe instructions which execute on the computer or other programmableprocessing apparatus provide steps for implementing the functionsspecified in the equation(s), algorithm(s), and/or block(s) of theflowchart(s).

Some or all of the methods and tasks described herein may be performedand fully automated by a computer system. The computer system may, insome cases, include multiple distinct computers or computing devices(e.g., physical servers, workstations, storage arrays, etc.) thatcommunicate and interoperate over a network to perform the describedfunctions. Each such computing device typically includes a processor (ormultiple processors) that executes program instructions or modulesstored in a memory or other non-transitory computer-readable storagemedium or device. The various functions disclosed herein may be embodiedin such program instructions, although some or all of the disclosedfunctions may alternatively be implemented in application-specificcircuitry (e.g., ASICs or FPGAs) of the computer system. Where thecomputer system includes multiple computing devices, these devices may,but need not, be co-located. The results of the disclosed methods andtasks may be persistently stored by transforming physical storagedevices, such as solid state memory chips and/or magnetic disks, into adifferent state.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Detailed Description using thesingular or plural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list. The word “exemplary” is usedexclusively herein to mean “serving as an example, instance, orillustration.” Any implementation described herein as “exemplary” is notnecessarily to be construed as preferred or advantageous over otherimplementations.

The disclosure is not intended to be limited to the implementationsshown herein. Various modifications to the implementations described inthis disclosure may be readily apparent to those skilled in the art, andthe generic principles defined herein may be applied to otherimplementations without departing from the spirit or scope of thisdisclosure. The teachings of the invention provided herein can beapplied to other methods and systems, and are not limited to the methodsand systems described above, and elements and acts of the variousembodiments described above can be combined to provide furtherembodiments. Accordingly, the novel methods and systems described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made without departing from the spiritof the disclosure. The accompanying claims and their equivalents areintended to cover such forms or modifications as would fall within thescope and spirit of the disclosure.

What is claimed is:
 1. A method for sensing a rotational position of a shaft having a longitudinal axis, the method comprising: determining a turn number of the shaft with a first magnet arranged in a non-contact manner with a first magnetic sensor to allow measurement of a linear position of the first magnet relative to the first magnetic sensor, the linear position representative of a turn number of the shaft; determining an angular position of the shaft within a given turn with a second magnet positioned at an end of the shaft along the longitudinal axis and arranged relative to a second magnetic sensor; and combining the turn number with the angular position to generate one or more output signals representative of a measured rotational position of the shaft.
 2. The method of claim 1, wherein the measured rotational position of the shaft is within a rotational range having a plurality of turns.
 3. The method of claim 2, wherein the turn number is determined with an M-bit resolution, and the angular position within the given turn is determined with an N-bit resolution.
 4. The method of claim 3, wherein the N-bit per turn angular position is substantially maintained for the measured rotational position throughout the rotational range of plurality of turns.
 5. The method of claim 4, wherein the combining generates an effective resolution of M+N bits over the rotational range of plurality of turns.
 6. The method of claim 2, wherein the plurality of turns includes more than two turns.
 7. The method of claim 6, wherein the value of M is selected to be 4 or less to allow determining of turn numbers up to
 16. 8. The method of claim 1, wherein the second magnet is arranged in a non-contact manner with the second magnetic sensor.
 9. The method of claim 8, wherein the second magnet includes a bipolar and diametrally magnetized magnet configured to provide variable orthogonal and parallel magnetic fluxes to the second magnetic sensor.
 10. The method of claim 8, wherein the second magnetic sensor is configured to operate in quadrature mode, the second magnetic sensor including a plurality of Hall-effect sensors, a plurality of magneto-resistive (MR) sensors, or a plurality of giant magnetic resistive (GMR) sensors.
 11. The method of claim 10, wherein the second magnetic sensor includes four sensors positioned in quadrature and configured to operate as sine-cosine sensors.
 12. The method of claim 8, wherein the one or more output signals includes one or more analog signals from the second magnetic sensor.
 13. The method of claim 12, further comprising processing the one or more analog signals to generate a digital signal representative of the measured rotational position of the shaft.
 14. The method of claim 13, wherein the generating of the digital signal is performed by an analog interface.
 15. The method of claim 14, wherein the analog interface and the second magnetic sensor are parts of, or disposed on, and application specific integrated circuit (ASIC).
 16. A multi-turn sensing apparatus, comprising: a rotation counter configured to determine a number of turns made by a shaft about a longitudinal axis, the rotation counter including a first magnet and a first magnetic sensor, the first magnet coupled to the shaft and configured to move linearly along a direction having a component parallel to the longitudinal axis when the shaft is rotated, the first magnetic sensor configured to sense the linear motion of the first magnet and determine the number of turns of the shaft; and an angular position sensor configured to measure an angular position of the shaft for a given turn, the angular position sensor including a second magnet and a second magnetic sensor, the second magnet mounted to an end of the shaft along the longitudinal axis and configured to rotate with the shaft, the second magnetic sensor configured to sense the rotation of the second magnet and determine the angular position of the shaft.
 17. The multi-turn sensing apparatus of claim 16, wherein the shaft is part of the apparatus and configured to be coupled to an external rotating device.
 18. The multi-turn sensing apparatus of claim 16, wherein the shaft is part of an external rotating device.
 19. The multi-turn sensing apparatus of claim 16, wherein the first magnet is arranged in a non-contacting manner with respect to the first magnetic sensor.
 20. The multi-turn sensing apparatus of claim 16, wherein the second magnet is arranged in a non-contacting manner with respect to the second magnetic sensor. 